The invention relates to a scanning device having an optical scanning system comprising a unit for repeatedly scanning a scanning surface of a record carrier by means of a first and a second scanning beam, the first and the second scanning beam forming a first and a second scanning spot on the scanning surface, which scanning spots move synchronously over the record carrier along a first and a second scanning path, respectively. The invention further relates to a recording and/or read apparatus comprising such a scanning device.
Such devices are known from U.S. Pat. No. 4,901,297. By means of the scanning device disclosed therein, the recording surface of a magneto-optical record carrier in the form of a tape, which surface corresponds to the scanning surface, is scanned by two scanning spots in a direction transverse to the longitudinal direction of the record carrier tape. In order to realise this scanning, two parallel laser beams are projected onto the record carrier via facets of a rotating polygonal mirror. The scanning spots formed on the recording surface by the two laser beams follow parallel scanning paths. The tape is moved in the longitudinal direction so that the recording surface is scanned along parallel scanning paths which are such that the path scanned by the first scanning spot is scanned by the second scanning spot during the next scan. The recording surface is erased during scanning by the first scanning spot. Subsequently, information is recorded in this erased part of the recording surface during scanning by the second scanning spot. This results in a track pattern of parallel information tracks whose track directions extend transversely of the longitudinal direction to the tape.
During recording, the track pitch (distance between the centres of two adjacent tracks) is not controlled. As a result of inevitable variations in parameters which influence the track pitch, for example variations in tape transport speed, the track pitch of the resulting track pattern will vary. Therefore, it is desirable that during recording information about the track pitch is available for the purpose of track pitch monitoring and/or control.